added flann based feature matching

Author: tejus-gupta

src/ImageFeatures.jl

@@ -4,6 +4,7 @@ module ImageFeatures
 
 # package code goes here
 using Images, ColorTypes, FixedPointNumbers, Distributions
+using FLANN, Distances
 using Compat
 
 include("core.jl")
@@ -24,6 +25,7 @@ export
     create_descriptor,
     hamming_distance,
     match_keypoints,
+    match_keypoints_flann,
     grade_matches,
 
     #Local Binary Patterns

src/core.jl

@@ -39,7 +39,7 @@ features = Features(boolean_img)
 features = Features(keypoints)
 ```
 
-Returns a `Vector{Feature}` of features generated from the `true` values in a boolean image or from a
+Returns a `Vector{Feature}` of features generated from the `true` values in a boolean image or from a 
 list of keypoints.
 """
 const Features = Vector{Feature}
@@ -59,7 +59,7 @@ function Keypoints(img::AbstractArray)
     map((ri, ci) -> Keypoint(ri, ci), r, c)
 end
 
-Keypoints(features::Features) = map(f -> f.keypoint, features)
+Keypoints(features::Features) = map(f -> f.keypoint, features)        
 
 const OrientationPair = Tuple{Int16, Int16}
 const OrientationWeights = Tuple{Float16, Float16}
@@ -87,7 +87,7 @@ function match_keypoints(keypoints_1::Keypoints, keypoints_2::Keypoints, desc_1,
     s_key = keypoints_1
     l_key = keypoints_2
     order = false
-    if length(desc_1) > length(desc_2)
+    if length(desc_1) > length(desc_2) 
         smaller = desc_2
         larger = desc_1
         s_key = keypoints_2
@@ -106,6 +106,55 @@ function match_keypoints(keypoints_1::Keypoints, keypoints_2::Keypoints, desc_1,
     matches
 end
 
+"""
+```
+matches = match_keypoints_flann(keypoints_1, keypoints_2, desc_1, desc_2, threshold = 0.1)
+```
+
+Finds matched keypoints with hamming distance value less than `threshold` using FLANN.
+"""
+function match_keypoints_flann(keypoints_1::Keypoints, keypoints_2::Keypoints, desc_1, desc_2, threshold::Float64 = 0.1)
+    smaller = desc_1
+    larger = desc_2
+    s_key = keypoints_1
+    l_key = keypoints_2
+    order = false
+    if length(desc_1) > length(desc_2)
+        smaller = desc_2::Array{BitArray{1},1}
+        larger = desc_1
+        s_key = keypoints_2
+        l_key = keypoints_1
+        order = true
+    end
+
+    ndims=length(larger[1])
+    nplarge=length(larger)
+    npsmall=length(smaller)
+
+    data=Matrix{Float64}(ndims, nplarge);
+    for i in 1:ndims
+        for j in 1:nplarge
+            data[i,j]=larger[j][i]?1:0
+        end
+    end
+
+    f=flann(data, FLANNParameters(), Cityblock())
+
+    matches = Keypoints[]
+    test=Vector{Float64}(ndims);
+    for i in 1:npsmall
+        for j in 1:ndims
+            test[j]=smaller[i][j]?1.0:0.0
+        end
+        idx, dist = nearest(f, test, 1)
+        if dist[1]/ndims < threshold
+            id_min = idx[1]
+            push!(matches, order ? [l_key[id_min], s_key[i]] : [s_key[i], l_key[id_min]])
+        end
+    end
+    matches
+end
+
 """
 ```
 grade = grade_matches(keypoints_1, keypoints_2, limit, difference_method)